(1) Field of the Invention
The present invention relates to a liquid crystal light control element that can be incorporated into personal digital assistants, notebook or laptop computers, and the like. The invention also relates to an optical device such as a liquid crystal display device, and an electric device such as a memory device, an electroluminescent device, an electrophoretic device and the like. The invention further relates to a method of producing such devices.
(2) Description of the Prior Art
Various liquid crystal display modes have been suggested as a display mode of a liquid crystal display device. For example, a twisted nematic (TN) liquid crystal, a super twisted nematic (STN) liquid crystal, a polymer dispersed liquid crystal, an in-plane switching (IPS) type liquid crystal device, and the like have been suggested. In all the display modes of a liquid crystal display device mentioned above, a liquid crystal (a liquid crystal and a polymer, in the case of a polymer dispersed liquid crystal device) is filled between a pair of substrates, and the liquid crystal is driven by applying an electric field to perform a display operation. In other words, liquid crystal display devices require a pair of substrates as an essential component. This is because in a liquid crystal display device, a light control element driven by applying an electric field is composed of a liquid crystal, which has a flowability, and therefore the liquid crystal needs to be enclosed between a pair of substrates.
However, conventional liquid crystal display devices have the following drawbacks:
1. In recent years, a reduction of the device weight has been demanded in order to apply a liquid crystal display device to personal digital assistants and the like portable information devices. However, at the present state of art, a sufficient reduction in weight of a liquid crystal display device has not yet been achieved. The reason for this is that the weight of substrates accounts for relatively a large rate of the weight of a liquid crystal display device. Therefore, a liquid crystal display device in which the substrates are eliminated, or a liquid crystal display device composed of only one substrate is desired.
2. A wide application of a liquid crystal display device to various appliances has been also demanded. In view of this, if a liquid crystal display device in which substrates are eliminated, i.e., a liquid crystal light control element, can be commercialized as a finished product, the range of application of a liquid crystal display device is broadened by incorporating the liquid crystal light control element into various types of appliances. Accordingly, there is a need for a novel liquid crystal light control element such that a liquid crystal light control element, which is a principle component in a liquid crystal display device, is separated from the liquid crystal display device and independently commercialized as a finished product.
3. In the case of a reflective type liquid crystal display device, a reflector is generally provided outside a substrate. In such a device configuration, there is a problem of parallax in display since the reflector and a liquid crystal layer are apart by a distance equal to the thickness of the substrate.
4. In a configuration such that a liquid crystal is filled between the substrates, when a display panel is depressed by for example an input pen means or the like, an unevenness in display is caused because of the decrease in a cell gap. This results from the fact that liquid crystal is a fluidic matter.
There is also a requirement of the reduction in a device weight for electric devices such as a memory device, an electroluminescent device, an electrophoretic device and the like devices.
In view of the foregoing and other problems in prior art, it is an object of the present invention to provide a novel liquid crystal light control element that can be incorporated into various appliances.
It is another object of the present invention to provide an optical device having only one substrate and an electric device having only one substrate, in which a reduction in the weight is achieved thereby, and to provide a method of producing such devices.
It is further another object of the present invention to provide an optical device free from an unevenness in display caused by depressing the display panel with an input pen means and the like, and to provide a method of producing the device.
These and other objects are accomplished, in accordance with a first aspect of the invention, by the provision of an optical device comprising a composite provided on a substrate, the composite comprising a polymer resin and a liquid crystal, the optical device wherein:
the liquid crystal is in contact with the substrate on a surface of the composite adjacent to the substrate,
the polymer resin constitutes the other surface of the composite such that a layer of the polymer resin covers the liquid crystal, and
a means for applying an electric field to the liquid crystal is provided.
As described above, the optical device (for example a liquid crystal display device) is configured by using only one substrate, and this achieves a reduction in the weight of the device. In a conventional liquid crystal display device, the use of two substrates is essential, but the weight of the substrates accounts for a large rate in the weight of the device. Accordingly, as in the present invention, a device configuration in which one of the substrates is eliminated achieves a significant reduction in the device weight in comparison with conventional devices.
It is to be noted here that the phrase xe2x80x9cthe liquid crystal is in contact with the substratexe2x80x9d is intended to include a case in which the liquid crystal is in contact with a thin film such as alignment layer and the like formed on the substrate, as well as a case in which the liquid crystal is directly in contact with the substrate.
In the above configuration, the liquid crystal mentioned above may be formed in the form of a plurality of droplets, and the droplets of the liquid crystal may be juxtaposed on the substrate so as to form a single layer structure.
The liquid crystal in the present invention is so configured that the liquid crystal makes contact with a substrate. Therefore, it should be construed that the term xe2x80x9cdropletsxe2x80x9d is intended to include such configurations as follows:
a configuration in which a bottom surface of the liquid crystal being in contact with the substrate has a substantially planar shape and a surface covering the bottom surface has a curved or hemispherical shape,
a configuration in which the bottom surface of the liquid crystal being in contact with the substrate has a substantially planar shape and the surface covering the bottom surface has a flattened shape, and
a configuration in which a bottom surface of the liquid crystal being in contact with the substrate forms, on the substrate, a polygonal shape such as a hexagon as well as a circular shape.
In addition, the shape of the liquid crystal may be a substantially hemispherical shape or a flattened shape having a substantially uniform thickness, and a diameter of a bottom surface of the liquid crystal may be larger than a thickness of the composite.
When an optical device is such that the liquid crystal has a substantially hemispherical shape as described above, a uniformity of the liquid crystal in the composite is attained. Thereby, an improved display performance is achieved. When an optical device is such that the liquid crystal has a flattened shape having a substantially uniform thickness as above, it is possible to prevent an occurrence of a coloring effect in a peripheral region of the liquid crystal, which is caused by a thickness variation of the liquid crystal.
In addition, a surface of the substrate may be subjected to a wettability controlling treatment, and a surface energy of the substrate may be larger than a surface energy of the liquid crystal. With such configurations, it is possible to make the liquid crystal be in contact with a surface of the substrate, and thereby the composite, which is a principle component in the invention, is attained. Hence, an optical device according to the present invention, which makes use of wettability, has a simple device configuration, and a reduction of the device weight is thereby realized.
An optical device according to the present invention may be configured as a twisted nematic mode optical device by treating the substrate by a horizontal alignment treatment and by adding a chiral agent to the liquid crystal. In addition, an optical device according to the present invention may be configured as an in-plane switching mode optical device by employing a means of applying an electric field in a direction parallel to a substrate plane.
In addition, an optical device according to the invention may be configured as a vertical alignment mode optical device, a scattering mode optical device, and further a reflective liquid crystal display mode optical device by providing a reflective electrode outside the composite. In particular, when a configuration of a reflective mode optical device is employed, it is made possible to solve a problem of a parallax appearing on a displayed image, which is caused in a conventional reflective liquid crystal display device employing two substrates, since a device according to the present invention has only one substrate.
In addition, a gas barrier layer may be provided on the polymer resin. This configuration prevents H2O, O2, and the like in an external environment from entering the device. For example, an SiOx layer may be employed for the gas barrier layer.
The present invention also provides, in accordance with a second aspect of the invention, an optical device comprising a composite provided between a pair of substrates, the composite comprising a polymer resin and a liquid crystal, the optical device wherein:
the liquid crystal is in contact with one of the substrates on a surface of the composite adjacent to the one of the substrates,
the polymer resin constitutes the other surface of the composite adjacent to the other one of the substrates such that a layer of the polymer resin covers the liquid crystal, and
a means for applying an electric field to the liquid crystal is provided.
In the above-described configuration, the polymer resin that covers the liquid crystal has a supporting structure with an arch-like shape between the substrates. Thereby, the polymer resin serves as a division wall for hindering a flow or a detachment of the liquid crystal. As a result, even when an outer surface of the substrate, i.e., a display panel, is depressed with an input pen means and the like, the outer surface is not bent and therefore no unevenness in display is caused.
In this configuration as well, the liquid crystal may be formed in a plurality of droplets, and the plurality of droplets may be juxtaposed on the substrate so as to form a single layer structure. In addition, the shape of the liquid crystal may be a substantially hemispherical shape or a flattened shape having a substantially uniform thickness, and a diameter of a bottom surface of the liquid crystal may be larger than a thickness of the composite.
In addition, a surface of the substrate may be subjected to a wettability controlling treatment, and a surface energy of the substrate may be larger than a surface energy of the liquid crystal.
In addition, an optical device according to the invention may be configured as a scattering mode optical device, and a reflective liquid crystal display mode optical device by providing a reflective electrode outside the composite.
In addition, at least one of the pair of the substrates may be a film substrate. This configuration enables the device to be a small-sized and lightweight device.
In addition, the film substrate may serve as a gas barrier. Thereby, it is made possible to prevent H2O, O2, and the like in an external environment from entering the device without separately providing a gas barrier layer.
The present invention also provides, in accordance with a third aspect of the invention, an optical device comprising a composite provided between a pair of substrates, the composite comprising a polymer resin and a liquid crystal, the optical device wherein:
the liquid crystal is present exclusively in a region in the composite adjacent to the substrate, and
a means for applying an electric field to the liquid crystal is provided.
As in this configuration, when the liquid crystal in the composite is present exclusively in a region in the composite adjacent to the substrate, the other surface of the composite is composed of the polymer resin. Accordingly, it is made possible to form an electrode as a means for applying an electric field on the other surface of the composite, and thus an optical device comprising only one substrate is provided.
The present invention also provides, in accordance with a fourth aspect of the invention, an optical device comprising a composite provided between a pair of substrates, the composite comprising a polymer resin and a liquid crystal, the optical device wherein:
the liquid crystal is present exclusively in a region in the composite adjacent to one of the substrates, and
a means for applying an electric field to the liquid crystal is provided.
As in this configuration, when the liquid crystal in the composite is present exclusively in a region in the composite adjacent to one of the substrate, the other surface of the composite is composed of the polymer resin. Hence, by using, of the pair of substrates, one being in contact with the polymer resin as a display panel of the device, the display panel is not bent even if the display panel is depressed by an input pen means and the like, an therefore an unevenness in display does not occur.
The present invention also provides, in accordance with a fifth aspect of the invention, a method of producing an optical device comprising the steps of:
treating a surface of a pair of substrates to control a wettability such that a wettability of one of the substrates by a liquid crystal is larger than a wettability of the one of the substrates by a prepolymer component, and a wettability of the other one of the substrates by the prepolymer component is larger than a wettability of the other one of the substrates by the liquid crystal,
filling a mixture comprising a liquid crystal material and a prepolymer between the pair of treated substrates arranged such that the treated surfaces of the substrates face each other, and
forming a composite by polymerizing the prepolymer in the mixture so as to phase separate a polymer resin and a liquid crystal, the composite comprising the liquid crystal and a layer of the polymer resin, the liquid crystal being in contact with the one of the substrates and the polymer resin layer being in contact with the other one of the substrates and covering the liquid crystal.
By the method as described above, an optical device in accordance with the second aspect of the invention is produced.
In the above method, the method of polymerizing the prepolymer may be either of a photopolymerization by irradiating with an ultraviolet ray and a thermal polymerization.
In addition, in the step of treating a substrate surface in the above-described method, only one of the substrates may be treated to control a wettability, instead of treating both substrates.
In addition, in the step of forming a composite in the above-described method, the liquid crystal may be separated in the form of a droplet, and a condition for separating the droplet of the liquid crystal may be such that the droplet of the liquid crystal has a diameter equal to or larger than a cell gap. By restricting the conditions for separating the liquid crystal, it is ensured that all the liquid crystal droplets make contact with one of the substrates. When the liquid crystal droplets make contact with one of the substrates, the droplets having a spherical shape deform into droplets having a hemispherical shape. Thus, it is made possible to form a composite in which all the liquid crystal droplets therein are in contact with the substrate. Further, by restricting the conditions for separating the liquid crystal such that a spherical liquid crystal droplet having a further larger diameter can be formed, the shape of the formed liquid crystal droplets become a flattened shape having a substantially uniform thickness.
In addition, a step of peeling off the other one of the substrates may be provided after the step of forming a composite, and by forming an electrode on a surface of the composite from which the other one of the substrates is peeled off, an optical device in accordance with the first aspect of the invention is produced.
The other one of the substrates may be, for example, a plastic substrate having a deformability.
In addition, the above-described method may further comprise a step of forming a gas barrier on a surface of the composite from which the other one of the substrates has been peeled off, and may further comprise a step of forming an insulating layer on the electrode provided on a surface of the composite from which the other one of the substrates has been peeled off.
The present invention also provides, in accordance with a sixth aspect of the invention, a method of producing an optical device comprising the steps of:
treating a surface of a substrate to control a wettability such that a wettability of the substrate by a liquid crystal is larger than a wettability of the substrate by a prepolymer component,
coating a mixture comprising a liquid crystal material and a prepolymer on the treated surface of the substrate, and
forming a composite by polymerizing the prepolymer in the mixture so as to phase separate a polymer resin and a liquid crystal, the composite comprising the liquid crystal being in contact with the substrate and a layer of the polymer resin covering the liquid crystal.
By the method as described above, an optical device according to the first aspect of the invention is produced with the use of only one substrate. Therefore, the step of peeling off one of the pair of substrates as in the method of the fourth aspect of the invention is made unnecessary.
In addition, in this method as well, the method of polymerizing the prepolymer may be either of a photopolymerization by irradiating with an ultraviolet ray and a thermal polymerization. In the case of photopolymerization by irradiating with an ultraviolet ray, it is preferable that the polymerization be performed in a nitrogen atmosphere. When the irradiation with an ultraviolet ray is performed in the air, oxygen in the air reacts with the prepolymer, hindering the polymerization. In order to avoid such an undesirable phenomenon, the photopolmerization by irradiating an ultraviolet ray is preferable to be performed in a nitrogen atmosphere, and thereby a problem of unpolymerization can be resolved. Furthermore, it is known that when the photopolymerization by an ultraviolet ray is carried out in a nitrogen atmosphere, the polymer comes out towards a surface of the composite. Therefore, it is made possible to produce, with the use of only one substrate, a composite comprising a liquid crystal being in contact with a surface of the substrate and a polymer resin that covers the liquid crystal.
The present invention also provides, in accordance with a seventh aspect of the invention, a light control element comprising a composite composed of a polymer resin and a liquid crystal, and a resin film formed on one surface of the composite, the light control element driven by applying an electric field to the composite, the light control element characterized in that:
in one surface of the composite, the liquid crystal is in contact with the resin film, and
a layer of the polymer resin constitutes the other surface of the composite such that the layer of the polymer resin covers the liquid crystal.
This configuration achieves a novel liquid crystal light control element. This liquid crystal light control element, which is a principal constituent element in a liquid crystal display device, is produced as a finished product, independent of the liquid crystal display device. The liquid crystal light control element can be incorporated into various appliances provided with a means for applying an electric field, and thus made into a liquid crystal display device. Thereby, the liquid crystal light control element can be suitably applied to a wide range of liquid crystal display devices.
The liquid crystal light control element may be configured such that the liquid crystal is formed in the form of a plurality of droplets, and the plurality of droplets are juxtaposed on the substrate so as to form a single layer structure. In addition, the shape of the liquid crystal may be a substantially hemispherical shape or a flattened shape having a substantially uniform thickness, and a diameter of a bottom surface of the liquid crystal may be larger than a thickness of the composite.
The present invention also provides, in accordance with an eighth aspect of the invention, an electric device comprising a composite provided on a substrate, the composite comprising at least a first substance being a solid substance and a second substance, the composite wherein:
the second substance is in contact with the substrate in a surface of the composite adjacent to the substrate, and
the other surface of the composite is composed of the first substance such that the first substance covers the second substance.
In the above-described configuration, the first substance may be such a substance as a polymer resin, a transparent substance, and a liquid glass. The second substance may be an electroluminescent substance. Further, the second substance may be a liquid crystal, a surface of the substrate may be treated by a wettability controlling treatment, and a surface energy of the substrate is larger than a surface energy of the liquid crystal.
The present invention also provides, in accordance with a ninth aspect of the invention, an electric device comprising a composite provided between a pair of substrates, the composite comprising at least a first substance being a solid substance and a second substance, the composite wherein:
the second substance is in contact with the substrate in a surface of the composite adjacent to one of the substrates, and
the other surface of the composite adjacent to the other one of the substrates is composed of the first substance such that the first substance covers the second substance.
As an example of the eighth aspect and the ninth aspect of the invention, a memory device is realized by employing, for example, a magnetic material or a ferroelectric material as the second substance. By employing an organic functional material as the second material, an electroluminescent device (an EL device) is realized. When the second substance separated on the substrate is a substance having flowability, an electrophoretic device is realized.
The present invention also provides, in accordance with a tenth aspect of the invention, a method of producing an electric device comprising the steps of:
treating a surface of a pair of substrates to control a wettability such that a wettability of one of the substrates by a first substance is larger than a wettability of the one of the substrates by a second substance, and a wettability of the other one of the substrates by the second substance is larger than a wettability of the other one of the substrates by the first substance,
filling a mixture comprising at least the first substance and the second substance between the pair of treated substrates arranged such that the treated surfaces of the substrates face each other, and
forming a composite comprising the first substance and the second substance by phase separating the mixture,
the step of forming a composite wherein:
the first substance is formed such that the first substance makes contact with the one of the substrates, and
the second substrate is formed such that the second substance makes contact with the other one of the substrates.
By the method as described above, an electric device in accordance with the ninth aspect of the invention is produced. In addition, by peeling off one of the pair of the substrates, an electric device in accordance with the eighth aspect of the invention is produced.
In addition, in the step of treating a surface of a pair of substrates, only one of the substrates may be subjected to a wettability controlling treatment.